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Chemical oxygen generator once ignited

Aviation Mechanic Airframe (AMA) practice question 14 of 15 on Environmental Systems. ACS element AM.II.G.K9 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic Airframe (AMA) practice mode.

Question bank updated 2026-09-22

QUESTIONOnce a sodium chlorate chemical oxygen generator has been ignited, what happens?

  1. AIt can be shut off by the flight crew.
  2. BIt burns until its supply is gone.
  3. CIt stops when the mask is removed.
Show the answer and explanation

Correct answer: B. It burns until its supply is gone.

  • A — incorrect There is no means of stopping a generator once lit, which is why it is described as an all-or-nothing oxygen source.
  • B — correct A lit sodium chlorate generator cannot be extinguished; it produces a steady flow of oxygen until it burns out, typically 10 to 20 minutes.
  • C — incorrect Generator output is independent of whether anyone is breathing from the mask; it continues until the candle is consumed.

BACKGROUND

Sodium chlorate produces oxygen as it burns, and formed chunks of it, called solid oxygen candles, are wrapped in insulated stainless-steel housings that control the heat produced. Ignition is often by a spring-loaded firing pin that releases a hammer to smash a cap and create a spark, though electric ignition by a hot wire also exists. Once lit, the generator cannot be extinguished and produces a steady flow of breathable oxygen until it burns out, typically 10 to 20 minutes. Solid oxygen generators are used mainly as backup oxygen on pressurized aircraft; they weigh about one-third as much as gaseous systems holding the same quantity of oxygen, and they have a long shelf life. A used generator must be replaced, which makes them costly for short-duration use.

STUDY TIP

Focus on why chemical oxygen suits a backup role: light weight, long shelf life, minimal maintenance, but no way to stop it once started. That trade-off explains most exam answers about these units.

KEY POINTS

  • A lit sodium chlorate generator cannot be extinguished and runs 10 to 20 minutes.
  • Generators weigh about a third as much as gaseous systems of the same capacity.
  • Used generators must be replaced, so they are reserved for backup use.

SOURCES

  • sources/ama-airframe/ch16.txt "Chemical or Solid Oxygen"
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SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-31B Aviation Maintenance Technician Handbook – Airframe, and 14 CFR part 43. Regulations and handbooks are revised; confirm details against the current edition.